1. Unit 4: Sensation, Perception and States of Consciousness
WHS AP Psychology
Unit 4: Sensation, Perception and States of Consciousness
Essential Task 4-1:
Discuss basic principles of sensation/bottom up processing with specific attention to sensory transduction, absolute threshold, difference threshold (Weber's Law), signal detection, and sensory adaptation.
Logo Green is R=8 G=138 B= Blue is R= 0 G=110 B=184
Border Grey is R=74 G=69 B=64

2. Perceptual Constancies
Sensation
Vision
The Eye
Theories
Hearing
The Ear
Other Senses
Smell
Taste
Pain
Gestalt Principles
Perceptual Constancies
Perception
Basic Principles
Visual Illusions
Depth Perception
We are here

3. States of Consciousness
Altered States of Consciousness
Waking Consciousness
Daydreaming and Fantasy
Sleep
Circadian Rhythm
Stages/REM
Dreams
Disorders
Drug-Altered Consciousness
Depressants
Hallucinogens
Stimulants
Hypnosis
Hidden Observer
Actor
Meditation
Substance Abuse

4. Essential Task 4-: Sensation/bottom-up processing
Outline
Sensation/bottom-up processing
Perception/top-down processing
Transduction
Absolute threshold
Difference threshold
Weber's Law
Signal detection
Sensory adaptation

5. Sensation & Perception
Outline
How do we construct our representations of the external world?
To represent the world, we must detect physical energy (a stimulus) from the environment and convert it into neural signals. This is a process called sensation.
When we give meaning by selecting, organizing, and interpreting our sensations, the process is called perception.
OBJECTIVE 1| Contrast sensation and perception, and explain the difference between bottom-up and top-down processing.

6. Sensation vs. Perception
Outline
Sensation
The experience of sensory stimulation
Perception
The process of creating meaningful patterns from raw sensory information

7. What do you see vs. what do you perceive?
Outline

8. What do you see vs. what do you perceive?
Outline

9. What do you see vs. what do you perceive?
Outline

10. What do you see vs. what do you perceive?
Outline

11. Bottom Up vs. Top Down Processing
Outline
Perception
Sensation

12. Bottom-up Processing
Outline
Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind.
Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.”

13. THE CHT Top-Down Processing
Outline
Information processing is guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations.
THE CHT

14. Example of Top-Down Processing
Outline
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15. The Basic Process Receptor cells
Outline
Receptor cells
Specialized cells that respond to a particular type of energy
Transduction-external energy is converted to neural signals.
Doctrine of specific nerve energies
One-to-one relationship between stimulation of a specific nerve and the resulting sensory experience
For example, applying pressure with your finger to your eye results in a visual experience
transparent protective coating over the front of the eye

16. Transduction
Outline

17. Absolute Threshold
Outline
Smallest detectable LEVEL of a stimulus.

18. Detection must be 50% of time.
Outline
Absolute
Threshold
Intensity No No No
Yes
Yes
Observer’s Response
Detected
Tell when you (the observer) detect the light.

19. Absolute Thresholds
Outline
Taste: 1 gram (.0356 ounce) of table salt in 500 liters (529 quarts) of water
Smell: 1 drop of perfume diffused throughout a three-room apartment
Touch: the wing of a bee falling on your cheek from a height of 1cm (.39 inch)
Hearing: the tick of a watch from 6 meters (20 feet) in very quiet conditions
Vision: a candle flame seen from 50km (30 miles) on a clear, dark night

20. Difference threshold The smallest detectable CHANGE in a stimulus
Outline
The smallest detectable CHANGE in a stimulus
Also called the just noticeable difference (jnd)

21. Difference Threshold
Outline
Difference Threshold: Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND).
Difference
Threshold No No
Yes
Observer’s Response
Tell when you (observer) detect a difference in the light.

22. Weber’s Law Stimulus Constant (k) Light 8% Weight 2% Tone 3%
Outline
Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. Weber fraction: k = dI/I.
Stimulus
Constant (k)
Light 8%
Weight 2%
Tone 3%

23. Our perceptions are organized by meanings that our minds impose.
Outline
We perceive the world not as it is, but as it is useful for us.

24. Sensory Thresholds Weber’s Law
Outline
Weber’s Law
States that the difference threshold is a constant proportion of the specific stimulus
Senses vary in their sensitivity to changes in stimulation
Envelop and coin demonstration.
More than just sensation it has to do with sales.

25. Signal Detection Theory (SDT)
Outline
Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). SDT assumes that there is no single absolute threshold and detection depends on:
Person’s experience
Expectations
Motivation
Level of fatigue

26. Signal Detection Theory
Outline

27. Sensory adaptation
An adjustment of the senses to the level of stimulation they are receiving
Ever forgotten you are wearing a watch?
Ever gotten used to a smell?
Then why don’t things disappear from your vision?
Outline

28. Outline